This invention relates generally to film packs usable in photographic cameras of the instant developing type. More particularly, it relates to film packs employing an improved yeildable supporting platform which supports the stack in such a manner that succesive topmost units are urged to the exposure station in a flat condition and are capable of being easily ejected therefrom.
Self-developing film units of the kind utilized in instant photography are typically housed in a film pack cassette having a yieldable supporting platform for supporting a stack of film units. These units have an image-receiving area bordered, in part, by a rupturable fluid pod and a trap at leading and trailing ends of the film unit; respectively. The spring tends to urge each topmost unit against the interior of a flat wall defining the aperture of the cassette. It is extremely important in these systems that the film units be in as flat a condition as possible when presented at a film focal plane. This is because a curved or bent film results in lack of image sharpness. Adequately, supporting these film units is relatively difficult given their physical characteristics. More specifically, because of their thin, flexible and uneven weighted and dimensioned nature the units tend to sag or bend easily. Sagging besides affecting flatness, inhibits proper picking of successive units to the pressure applying rollers. This also hinders exiting of the units from a cassette exit slot. Another factor relating to the physical characteristics of the film units is that the biasing force on the units cannot be too strong, otherwise rupturing of the topmost film unit against the cassette housing may result. Also, if the force is too great jamming of the unit against the housing may cause film bending or buckling, thereby making it difficult to eject.
Representative examples of film packs having biasing platforms in film packs having multiple film units are described and shown in the U.S. Pat. Nos. 3,543,662; 3,595,661; 3,707,116; 3,821,049; 3,682,076; and, German Pat. No. DE 33 40 175 Al.